In recent years, to realize miniaturization and surface-mounting, a surface acoustic wave device is made by flip-chip-connecting a transducer face of a surface acoustic wave element to a base board (circuit board) having wiring patterns and facing the transducer face. To make mass production easy, the base board is made from a multi-piece board (base-board aggregate) which is divided into individual pieces after predetermined processes.
Sealing methods for surface acoustic wave elements include a method of covering an element with a cap-like sealing material and bonding the sealing material to a base board and a method of bonding surface acoustic wave elements in a wafer state not individually divided to a multi-piece board and collectively dicing the surface acoustic wave elements in the wafer state, the base-board aggregate, and an adhesive bonding them together, into individual pieces.
However, the former method requires the cap-like sealing material to be prepared separately and newly needs the bonding process on the base board. Further, a new process is needed to hardening the adhesive to bond the cap-like sealing material and base board together. In this way, the former method increases extra processes and reduces productivity.
On the other hand, the latter method needs a process of simultaneously dicing the surface acoustic wave elements and base boards that involve different kinds of material. In this process, the surface acoustic wave elements may have problems of breakage, chipping off, or separation between parts, to provide insufficient sealing property and deteriorate yield.